Investment Securities - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2015 USD ($) Bond	Dec. 31, 2014 USD ($) Bond	Dec. 31, 2013 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Average yields (taxable equivalent) on securities			2.48%	2.40%
Market value of securities			$ 8,600	$ 8,500
Securities sold under repurchase agreements			7,161	6,012
Other-than-temporary impairment charge					$ 288
Proceed from disposal of auction rate securities			13,540	3,810
Company's investment in Federal Home Loan Bank stock			2,000	1,900
Company's investment in Federal Reserve Bank stock			$ 505	$ 382
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond			5	13
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond				3
Municipal Securities
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond			17	29
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions | Bond			1
Auction Rate Security
Schedule of Available-for-sale Securities [Line Items]
Face amount of security sold		$ 1,200
Percentage of Auction rate securities with provision		50.00%
Proceed from disposal of auction rate securities	$ 912